This invention relates to a novel rotary control valve with new joint methods and flow control mechanisms, inline-repairability and fully metal seals more particularly to a triple offset butterfly valve or ball valve with those novel features used for on-off and flow fluid controlling under multiple extreme conditions or in severe services; such as the rocket engine fuel control system with highly oxidative fluid under extreme temperature of 1350 F, the integrated gasification combined cycle (IGCC) under high temperature and pressure, Fluid Catalytic Cracking Unit (FCCU) under high temperature over 1200 F with hard diamond like catalytic particles, shale fracking process under extreme high pressure and high velocity fluid with solid particles and corrosive additives, other applications with flow fluid with high viscosity in field of chemical plants, or conventional power plants, refiners and oilfield, or other critical applications for products life lasting 5 to 30 years like deepsea flow control systems and nuclear power plants and for the applications of millions cycles like jet or rocket turbine engine fuel delivery systems with high velocity fuel fluid mixed with highly oxidative gas under temperature 1365 F or higher without failure.
This valve comprises a body with a flow port and a stem bore, a stem keyed with a disc is disposed in the stem bore to rotate the disc between open and closed positions, noise/cavitation reducing trims are installed in both ends of the flow port to reduce cavitation or noise, this valve is fully sealed in the stem by a simple, reliable metal K ring with laminated metal packings and in the port by full metal wave seat rings instead of conventional laminated seat with metal rings, graphite rings and gasket. It has a simple base structure with versatile configurations for various applications and is easy for manufacturing and repair, yet robust and reliable.
Conventional triple offset butterfly valves were developed in 1960s, but since then most features have not been changed, historically there is misunderstanding that the triple offset mechanism can solve all rotary metal seal problems, technically it only solve the rubbing problem to a some level, the rubbing happens between the conical seat and conical seat ring during rotation between 0-90 degrees, it damages the seat and seal ring and cause high torque, leak and seat prematurely to wear out and like the most ball valves, 98% of all existing triple offset butterfly valves only solve this rubbing problem between 0-86 degrees at best, it means that the rubbing still happens between 87 to 90 degrees, only 3 degrees but with 60%-100% contact area, it still causes damage on the seat, so how to reach 0-89.95 or 0-89.99 degrees of disengagement becomes an art and a knowhow or trade secret, there are other seven existing problems which have nothing to do with triple offset mechanism (1) metal to metal seat seal, there is no good solution so far, either the original solid seat has high leakage under ANSI class III leakage or the laminated seat with metal rings glued with graphite rings has ANSI class VI leakage at a new condition, but (a) the seat is easily damaged either by flow or a mating seat ring, it is required that high preload is to secure a seal between the seat and disc or body with additional graphite gasket and constantly replacement for the seat (b) the seat can not be used on highly oxidative flow applications when temperature is over 850 F (c) high seating torque, on average, operating torque for triple offset butterfly valves with the laminated seat is at least as twice high as that of the same size of double offset butterfly valve due to high pre-bolting on the seat as well as the nature of seat structure, moreover the actuation forces are unpredictable at a closed position, so it is difficult to automate (2) axial bolting joint between retaining ring and seat ring on the disc, most conventional seal ring joint devices employ direct screws or sleeve to secure seal rings, such a method not only produces uneven pressing forces on seal rings and seats, but also has a lower reliability with multiple bolting and high probability of screws falling into pipelines under vibration or high cycle conditions, according to Failure Modes and Effects Analysis (FMEA), such a structure has the highest severity in high vibration, high temperature applications like turbine or jet engine systems, a risk of bolts falling in a pipeline system is very high due to vibration, quick cycle and high temperature creep (3) the graphite stem seals, the stem seal with graphite needs excessive packing force and constant readjustment or replacement of packing, moreover the actuation forces are unpredictable, so it is difficult to automate, in case of subsea flow devices or nuclear power plants, or jet engine fuel delivery system, the constant readjustment is impracticable (4) key/pin joint between stem and disc, this conventional joints greatly reduce the strength of stem with high stress concentration on disc hub and stem as well as eliminate the freedom for the stem and disc expansion under high temperature and pressure by a pin joint or have freedom of movement but cause loss motion and backlash with a key joint, as a result, either the joint method can cause premature damage on seats and seat leak (5) lack of simple mechanism to reduce the cavitation and noise when the valve is used to throttle the flow (6) unidirectional seal and stem galling under high thermal cycle or high temperature, although many triple offset valve makers claim that their valves are bidirectional, in fact the upstream seal is tended to move the seat away from the body seal ring, moreover there are cumulative clearances between bearing inside diameter and stem, stem and disc hub, body bearing hole and bearing outside diameter, sometime after sudden closing, the valves start to leak due to the clearances, so the current solution is to tight the clearances, as a result, stem will tend to gall with bearing under high temperature or thermal cycle, in short those problems greatly reduce potential usage of the triple offset butterfly valve and prevent it from getting more market share (7) Inline reparability, in some applications, the valves are fully welded with the pipe line, so it is impossible for inline repair, so replacement for the whole valve or offline repair can cost lots money for customers.
In order to overcome the disadvantages or solve the problems of the conventional triple offset butterfly valve, many efforts have been made in the prior arts. The efforts in five fields were made to improve the conventional valves in the prior arts, but those works within a limited scope.
The first field is for improving the seat seal, many efforts were made, especially in metal to metal seat seal in high temperature, cryogenic environments or for highly abrasive or erosive fluid applications. The significant efforts were made by Karl Adam as shown in U.S. Pat. No. 3,442,488 (1969), a butterfly valve with a triple offset arrangement for reducing rubbing between a seat and a seal ring or disc and increasing the life of the seat seal, but the seat seal itself was not improved and has a solid surface vs. a solid surface seal, such a seal causes high operation torque, leakage and requires expensive precision machining and assembly. U.S. Pat. No. 4,667,929 to Franco Narduzzi (1986) discloses a similar offset arrangement on a ball valve, a seat seal is provided with a solid surface on a body against a solid surface on a ball, a seal ring on the ball is made out of a composite metal material with heat resistant and deformable natures, in the reality such an ideal material is difficult to make, moreover a secure means was not clearly disclosed, the secure means is the other key factor for a good metal seal under high temperature, without a good seat secure means, a stable metal seat seal is impossible. U.S. Pat. No. 3,905,577 to Anatole N. Karpenko (1975) discloses a replaceable laminated seat against solid surface of disc, this seat would be a good choice for a metal to metal seat seal, but the bolts and rivets are used as a secure means completely constrain the seat thermal expansion under high temperature, as the temperature increases, the seat will deform and loosen a seal. U.S. Pat. No. 5,377,954 to Siegbert Adam et al (1995) discloses a metal seat seal which has a solid surface vane against a flexible seal ring assembly, the flexible seal ring assembly has multiple rings with one support end and an unmatched seal surface against the vane, such a seat seal is stronger and more stable than seat seal in U.S. Pat. No. 4,037,819, but the seat seal still is unstable under high pressure or high cycle condition and also creates a new problem which is fluid seeping between the rings, although edge welded by a laser welder is provided as a remedy, such a weld process brings out another problem which is deformation of seal ring after welding, such deformation can generate more leakage on external surfaces of the ring, above all, the seat seal is unstable and vulnerable to fluid contamination and any point damage on the seal. U.S. Pat. No. 5,871,203 to Jerry Gassaway (1999) shows a widely used, laminated seat ring as a replaceable seat ring, but the replaceable seat ring without a secure means has a disadvantage in high temperature or high cycle environments, the different thermal expansion between a body and the seal ring can cause leakage through the seat ring. In short all efforts in the prior arts never address or recognize the fundamental problems—laminated seat seal mechanism, rigid flat ring deformation structure with weak graphite rings between them.
The second field is for improving the joint between the seat and the retaining ring. A conventional mechanical joint means for retaining a seat seal assembly on a valve member or body is accomplished by a retaining ring and multiple bolts as shown in U.S. Pat. No. 6,079,695 to Jerry Gassaway (2000), such a mechanical joint means requires precision drilling and tapping as well as tedious bolting process, any uneven bolting by manual operation or other process can cause a seat leak and heavy seating and unseating torques specially in large size valves or in high temperature environments, more importantly this mechanical joint means has a high risk of bolts falling into a pipeline system and is prohibited for using in the engines and turbines or other highly vibrated conditions, so a more reliable retaining device was developed as shown in U.S. Pat. No. 5,692,725 to Hans-Jurgen Fehringer (1997), the retaining device has smaller operating holes which prevents screws or bolts falling into a pipeline system, but the complicated retaining ring can be used only on a stationary body and not on a movable valve member, such a retaining device does not have a self lock, so any reaction force by a high vibration or uneven point forces by screws or bolts can cause screws loose and a seat leak. the fundamental disadvantage for axial bolting method is the direction of the seat loading is the same as that of bolting, so any disengagement between bolt thread and thread hole caused by a creep or vibration will soon amplify, many tests indicate without self lock mechanism, the bolting is not safe under high vibrations and temperature conditions.
The third field is for improving the stem seal packing. A packing device is one of those efforts shown in U.S. Pat. No. 4,886,241 to James R. Davis et al (1989) and U.S. Pat. No. 4,394,023 to Alberto L. Hinojosa (1983) disclose stem seals with graphite packing for high temperature applications, but the stem packing seals require more packing force and constant readjustment. A survey shows that 50% of the control valve failures are contributed by excessive stem packing force, the efforts to improve the stem seal are to add more stem seal packing sets, more seal force with more storing energy to both rotary and reciprocal stems. A live load packing device is one of those efforts shown in U.S. Pat. No. 5,230,498 to Charles W. Wood (1993), U.S. Pat. No. 5,503,406 to Leonard T. Armstrong (1996) and U.S. Pat. No. 5,860,633 to Ryan E. Murphy et al (1999). Those packing devices are not only expensive, inefficient and unsuitable for temperatures over 460 F, U.S. Pat. No. 6,202,668 to Robert E. Maki (2001) and U.S. Pat. No. 4,082,105 to Hebert Allen (1978) show fire-resistant stem seals. The fire-resistant stem seals are provided with a first PTFE seal and a secondary metal seal, in case of fire or temperature elevation, the secondary metal seal will replace the first PTFE seal, but in reality such a stem seal proves to be unreliable and has high leakage. In short, those prior arts in the stem seal field have common disadvantages: Inefficiency of packing loading. According to the Hook law and Poisson ratio, only about 30% of axial force in most materials is converted to radial displacements of the packing which helps fill in the gap between the stem and the packing, in addition of frictions, lower density or material creeps under high temperature, the efficiency of the conversion even becomes worse about 10-20%, so the conventional axial loadings for radial seal packing are inefficient and expensive to produce. The stem packing is one of those efforts shown in U.S. Pat. No. 4,886,241 to James R. Davis et al (1989) and U.S. Pat. No. 4,394,023 to Alberto L. Hinojosa (1983) disclose stem seals with graphite packing for high temperature applications, but the stem packing seals are subject to more packing force and constant readjustment. U.S. Pat. No. 7,004,452 to Chatufale (2006) shows C ring seal for gate valve, but it is unidirectional and not for high temperature, while U.S. Pat. Application No. 2011/0084456 A1 reveals a metal C ring with an insert for high temperature flange seal application, but the C ring only is used for static seal in flanges.
The fourth field is for improving the mechanical joint between stem and disc U.S. Pat. No. 4,483,513 to Anthony C. Summers (1984) and U.S. Pat. No. 4,828,221 to William B. Scobie (1998) disclose improved joints between a stem and a valve member, but the disadvantage is that the joints eliminate the stem axial freedom, the elimination can force thermal expansion to damage a seat or cause the stem deformation and a seat leak under high temperature, a conventional solution to the problem is to employ a key joint as shown in U.S. Pat. No. 6,079,695 to Jerry Gassaway (2000), but the key joint weakens the two hubs where the highest stress and stress concentration are located and torques are unevenly transferred, moreover the key joint requires an expensive broaching process for keyway. U.S. Pat. No. 6,029,949 to Robert Joseph Brown et al (2000) shows a plate and bolts for securing a stem on a vane, the design with the plate and bolts can further weakens the stem and vane and adds the cost for materials as well as machining, and there is a high risk of the plate and bolts falling into a pipeline system under high temperatures or high vibration conditions, such a design is prohibited in the turbine and engine systems, finally US 2008/0203346 A1 to Jianchao Shu (2008) shows the two key joints between the stem and disc, but the design cause high stress concentrations on the stem and motion loss.
The fifth field is for developing special disc or trim to reduce the noise and cavitation, for example, in U.S. Pat. No. 6,338,468 to Ogawa, et al. (2002) an enlarged section of valve body was employed to reduce cavitation, it is simple and low cost but in small opening, the cavitation still exists, many cases indicate the wall of the enlarged section is first damaged and flow penetrate the wall and cause leak, finally a valve application—is shown in U.S. Pat. No. 4,007,908 to Paul. V Smagghe.
In short, all efforts in the prior arts never address or recognize needs for replacing the axial retaining ring bolting or the laminated seat with metal and graphite stem seal and for developing full metal seat and stem seal under high temperature and fundamentally reducing the operation torque, most efforts are focused on easing the consequence rather than finding the root of cause, finally other inherent problem for butterfly valve is the upstream load support by the stem rather than the stem and seat like ball valve or gate valve, it causes unidirectional seal in most of the butterfly valves if the stem is not properly constructed.
So the flow control industry has long sought means of improving the performance of butterfly as well as rotary valve, improving the stem seal, creating a robust bidirectional seat seal, enabling the valve to handle various flow under multiple extreme conditions.
In conclusion, insofar as I am aware, no such butterfly or such rotary valve is formerly developed with fully metal sealed seat, highly reliable seat retaining device without high preload and risk of bolt falling into a pipeline system, easy manufacturing at low cost they can be used for controlling bidirectional fluid between full opening and full closed with no or less cavitation and low noise under multiple extreme conditions or severe service.